In prior art, telecommunication switching systems that communicated a large number of calls between a large number of telecommunication links, the problem of assuring that reliable timing information is distributed throughout the telecommunication switching system to port circuits interfacing to the telecommunication links has always been of major concern. In general, the prior art has solved this problem by utilizing duplicated dedicated timing paths on hardwired links from a central timing unit to the port circuits. Whereas the prior art telecommunication switching systems did provide a solution to the problem of distributing timing, this solution has many problems. The first problem is that setting up dedicated duplicated timing paths from a central control unit to the port circuit adds greatly to the cost and complexity of the telecommunication system. Further, the reliability is not greatly increased since the failure of two paths results in one or more port circuits not having timing information and being unable to function. Further, failures of the active timing source would necessarily cause timing and transmission interruptions.